Injection molding machine clamping unit

These functions must be performed automatically under conditions that ideally should result in a high quality and cost-effective part. Injection molding machines have two principal components to perform the cyclical steps in the injection molding process. These are the injection unit and the clamp unit (Figure 11.4). We now describe the operation of the various units of the injection molding machine... 

The operation of the injection and clamp units and other components of the injection molding machine (opening and closing of the mold and melting and injection of the polymer material) requires power, which is supplied by an electric motor. The orderly delivery of this power depends on auxiliary systems the hydraulic and control systems. The hydraulic system, the muscle for most maehines, transmits and controls the power from the electric motor to the various parts of the maehine. Maehine functions are regulated by a careful control of the flow, direction, and pressure of the hydraulic fluid. The elements of the hydraulic system for most injection molding machines are essentially the same fluid reservoir, pumps, valves, cylinders, hydraulic motors, and lines (Figure 11.8). 

The size of injection molding machines is usually specified in terms of injection capacity and clamp force. These factors are not directly related. Other important variables are the L D (length to diameter) ratio, barrel size, plasticizing rate, injection rate, and injection pressure. Major components of injection molding machines include the injection unit, the clamp unit, and the machine base which contains the power and control units. 

The main component of an injection-molding machine are (1) the injection unit which melts the molding material and forces it into the mold (2) the clamping unit which opens the mold and closes it under pressure (3) the mold used and (4) the machine controls. 

A typical arrangement for a direct screw-transfer injection-molding machine for thermosets is shown in Figure 2.16. The machine has two sections mounted on a common base. One section constitutes the plasticizing and injection unit, which includes the feed hopper, the heated barrel that en closes the screw, the hydraulic cylinder which pushes the screw forward to inject the plasticized material into the mold, and a motor to rotate the screw. The other section clamps and holds the mold halves together under pressure during the injection of the hot plastic melt into the mold. 

An injection molding machine is used. The clamping unit is used as a press and preplasticizing is done in the injection unit. With this technique, much more precise feeding of the preplasticized mixture keeps the molding tolerances down. 

The toggle lever clamping unit is now the predominant mechanical system for injection molding machines. It is not a purely mechanical system in the strictest sense, because hydraulics are also used for the movement of the toggle lever in this system. In principle, however, it is a mechanical system. 

The Injection Molding Machine (Lesson 2) The Plasticating and Injection Unit (Lesson 3) The Clamping Unit (Lesson 5)... 

The text focuses on many very important practical aspects of injection molding not (usually) found in treatments of injection molding intended for American engineering students. This includes the design of machine clamping units and hydraulic systems as well as the interaction of the plasticating and mold sections of the machine. Engineering students as well as technicians will find many sections of this book worthy of serious study. 

Any injection molding machine (Fig. 3) can be broken down into the following basic components (1) injection units, (2) clamping unit, (3) control system, and (4) tempering devices. The process of injection molding typically consists of the following steps ... 

The purpose of the injection unit is to heat and melt the polymer, inject the melt into the cavity, and apply pressure during the cooling phase. The most common type of injection molding machine is the reciprocating screw. In this type of machine, the screw rotates to plasticize the polymer, moving backward to deposit a volume of polymer melt ahead of the screw (shot). Once the correct shot size has been built, the screw then moves forward to inject the melt into the mold. Injection molding is a discontinuous process, and the clamping unit allows for the mold to open and close for part removal and to provide pressure as the cavity is filled. This is depicted in Fig. 1.19. 

Injection-molding machines have three components the injection unit, the clamping unit, and the control system. The injection unit plasti-cates and injects the polymer melt while the clamping unit supports the mold, opens and closes the mold, and contains the part ejection system. Typically different injection units can be assembled with the same clamping unit. 

Injection molding machine (Figure 6.1) consists of an injection and plastication unit, mold clamping unit, and hydraulic and control unit. In the injection unit, the polymer is melted by heating and shearing. The... 

In most cases, the compression movement is done by the clamping unit of the injection-molding machine. Modern machines with hydraulic or toggle clamping units are able control the position and the... 

In the injection molding machine shown in Figure 13, the clamp unit is on the left and the injection unit on the right. A mold is shown in position between the platens of the clamp unit with one half of the mold fastened to the fixed platen and the other to the movable platen. When the mold is opened, the movable platen moves away from the fixed platen and the molded part can be removed. After part ejection, the mold is closed in preparation for the next injection cycle. In contrast to extrusion, the screw in the injection imit rotates only during part of molding cycle. When the screw turns, it pumps melt forward. The rearward movement of the screw is controlled by the placement of a limit switch, which stops the hydraulic motor. The maximum length of reciprocation is approximately three screw diameters. The shot size is directly proportional to the amoimt of screw... 

Figure 5.1 Major components of an injection molding machine showing the extruder (reciprocal screw) and clamp units [1]...

FIGURE 1.3 Injection molding machine in typical 3-platen design with toggle clamping unit, without mold... 

An injection molding machine (Fig. 7.1) can be divided into six components plastification/injection section, clamping unit, mold including the runner system, control system, and tempering devices for the mold. The most important part of the process is the mold, which is made of at least two parts to allow ejection (demolding) of the molded part. The injection molding process can be divided into six steps. Table 7.1 presents the main function of each step. 

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